High voltage switching converters, such as boost converters, are used for a wide array of applications, including backlight applications using strings of LEDs, for example. For appropriately controlling such voltage converters, it is essential to have access to an indication of the current flowing through the switching node (LX node) of the voltage converter (i.e. through the (high power) output device of the voltage converter). On the other hand, the switching node must not be directly connected to low voltage devices (i.e. devices that are not high voltage tolerant) typically used in controlling voltage converters, such as comparators. The reason is that during the non-conducting phase of the pass device, the voltage at the switching node rises to very high values, especially for boost converters, which would damage or destroy the aforementioned low voltage devices.
To address this issue, a blanking switch might be provided between the switching node and the low voltage device in question to isolate the low voltage device from the switching node while the pass device is in the non-conducting state. Typically, such blanking switches are implemented by transistors. These transistors should either be isolated devices and would require a large number of additional layers for implementation, or non-isolated but should be able to operate at conditions when the source-bulk voltage is above zero. Thus, depending on the specific mode of operation of the blanking switch, implementation thereof by a transistor may be difficult and costly, or even impossible, especially in cases in which the transistor may not be operated in a mode in which the source-bulk voltage is above zero. Moreover, especially for boost converters, the transistor implementing the blanking switch might not operate reliably (i.e. cease to operate or introduce inacceptable errors) at low supply voltages and/or high input currents.